1. Field of the Invention
The present invention relates to safety devices for the upper ends of ladders.
2. Brief Description of the Prior Art
Accidents involving ladders, such as both portable extension ladders and non-extension ladders, can occur when the ladder shifts either because the climber is off balance to one side of the ladder, or because the climber accidentally moves the ladder when climbing off or onto a roof. The most dangerous time when using a ladder to descend is when stepping off of a roof onto a rung of the ladder. The climber is precariously perched, and must cautiously move himself with one foot on the roof and the other on the ladder before bringing the other foot onto the ladder. Standard portable ladders extend above the roof line and the climber must swing step around the extension to exit the ladder.
Additionally, a climber may lose a hand grip or his foot may slip off of a rung, or his foot may engage another object while climbing any of which may result in the climber falling, Ladder falls generally result in serious injury, and often result in death or paralysis.
Various solutions have been proposed to make the ladder more stable and ladder climbing safer. Inman, U.S. Pat. No. 8,439,163, fixes a ladder shoe to extend away from the ladder to engage a gutter. This shoe extends outwardly from the ladder. It limits how far the extension ladder can be collapsed, and also makes stacking the ladder more difficult for storage. Hastreiter, U.S. Pat. No. 6,394,229, proposes curved pole extensions bolted to each side rail of the ladder with a series of clamps. The distal end of each pole has a foot resting on the roof surface. These pole extensions must be carefully mounted on the outside of the ladder side rails each time the ladder is used. Otherwise the ladder is very cumbersome to move about or store.
The clamping required by Hastreiter is time consuming to install. While the pole extensions permit a walk-through climbing on and off the ladder, they are also intended to keep the ladder rails from contacting a gutter. This creates a space between the side rails of the ladder and the roof or roof gutter. In so doing, the pole extensions must bear the entire weight of the climber at an obtuse angle which requires them to be strong enough to hold against the bending forces thereby increasing their cost. Also, such pole extensions generally reduce the load capacity of the ladder.
Gabriel, U.S. Pat. No. 8,136,632, creates a step through extension ladder with a collapsible platform at its upper end. The platform collapses into a rung-free area at the upper end of the ladder side rails. When extended, this platform rests on the pitch of a roof with the ladder side rails resting against the roof edge or gutter. This requires a custom ladder re-configuration.
It is has long been suggested for safety, a ladder when leaning against a building or platform, is to be at an angle of about 75 degrees from horizontal. This means that the ladder side rails of each of the above ladders are pitched at an angle of about 15 degrees from vertical when above the roof or platform. This pitch makes climbing back from the roof onto the ladder safer. A steep pitch may promote fall back. A lesser pitch may produce slide out or “pancaking.”
Ellis, U.S. Pat. No. 6,095,283, shows a vertically upright ladder, permanently attached to a building, with a walk-through design having a wider ladder profile in the walk-through section at the top of the ladder. Two box-shaped elongate sleeves slide down over the top ends of the ladder side rails which side rails, are flared outward to widen the opening between side rails sufficiently to accommodate a climber and a plurality of inwardly extending horizontal grab rungs. The sleeves are positioned above the side rail flaring and secured to the side rails once in position. The location of the top of the sleeves is proximate to the top of the ladder side rails. The permanently flared outward side rails create an awkward structure for moving about and when storing the ladder.
Ellis, U.S. Pat. No. 6,347,685, shows a vertically upright ladder for permanent attachment to a structure with a walk-through area having two handhold cages providing recommended horizontal grab bars secured permanently to the top end of a respective ladder side rail. For ladders with flared out side rails, the grab cage is attached to the inside face of each side rail. For straight rails, the grab cage is attached to the outside face of each side rail.
Walk-through ladders have the advantage of providing a safer transition for the climber from the ladder to a roof and from a roof to the ladder. Permanently attached vertical walk-through ladders as shown by Ellis provide a safer transition region for the climber. The climber can first grasp one of the grab bars within box-like frameworks while safely standing on the roof. He can then turn and additionally grasp the second cage. While safely gripping both cages he can step onto the first ladder rung and then begin to transfer his hands to the grab bars.
OSHA regulations require that the base of an extension ladder, which OSHA considers as a portable ladder, be positioned away from the structure against which the extension ladder rests at a distance of about one-fourth of the working length of the ladder. That equates to about an angle of 75.5 degrees from the horizontal. OSHA regulations also state that no ladder should be used to gain access to a roof unless the top of the ladder shall extend at least three feet above the point of support. OSHA also wants each climber to face the ladder the entire ladder distance when climbing up or descending down, and to maintain a three-point control (two hands and a foot or two feet and a hand) resulting from holding rungs horizontally is much stronger and safer than holding side rails where a climber's hand can slide when on a ladder.
Because of the walk-through configuration at the top of the ladder, walk-through ladders are difficult to store and difficult to stack for travel on a vehicle. It is therefore desirable to provide a walk-through configuration at the top end of an extension ladder which is easily removable when the ladder is to be stored or stacked.
As safety is the first concern, it is desirable to provide a removable walk-through structure for a ladder which can be securely attached to the ladder upper end when the ladder is in use, and is easily removed when the ladder is to be stored or stacked for travel on a vehicle, or moved about.
It is also desirable that this structure is embodied in a safety device which can be easily attached to and removed from a standard ladder, such as a standard extension ladder.
Additionally, it is desirable to provide such a walk-through safety device which does not require any modification of a standard extension ladder, albeit, the walk-through safety device will be sized for the size of the ladder side rails which can vary with the materials from which the ladder is made, e.g., steel, aluminum or fiberglass, and in some cases wood, and for a specific ladder length and capacity ladder.
It is also desirable to have the walk-through safety device include a grab bar (handhold) cage, which will not interfere with the movement of a climber, and where the orientation of the safety grab (handhold) cage is upright and the handholds are horizontally oriented at the recommended spacing, when the ladder properly rests against a structure. The horizontal rung hand hold is intuitive for most climbers to grip and hold successfully in a dynamic fall. A fall become “dynamic” once a body is in motion. Once a fall has begun, grabbing a portion of a ladder results in forces on the hands which are increased greatly, making arrest difficult. If the handhold (rung) is horizontal, sliding is avoided.